BANGKOK, Dec. 2 -- Thailand's government collapsed Tuesday after the nation's Constitutional Court banned the prime minister from politics and dissolved three parties in his ruling coalition, delivering a partial victory to opponents, whose protests paralyzed the country's airports and raised fears of mass violence in Bangkok.

[The ruling against Somchai Wongsawat on charges of vote-buying and other election irregularities prompted anti-government activists to lift their siege of the Suvarnabhumi and Don Muang airports on Wednesday, the Associated Press reported. The protesters had occupied the airports in their drive to remove Somchai's administration from office.]

But there were signs Tuesday that Somchai's allies would not relinquish power. His deputy, Chavarat Charnvirakul, became the acting prime minister, and the coalition formerly headed by Somchai retained its substantial majority in parliament. The coalition is looking to form a new government with fresh leadership early next week, a move that anti-government leaders said would spur more protests.

"If a puppet government returns or a new government shows its insincerity in pushing for political reform, we will return," said Sondhi Limthongkul, one of the group's leaders.

It was not clear why the anti-government People's Alliance for Democracy, or PAD, pulled back with only part of its agenda fulfilled. But even before Tuesday's verdict, it had come under increasing pressure as its demonstrations wreaked havoc on Thailand's vital tourism industry and threatened to push the country into recession.

The opposition's decision to cede ground could mitigate the anger of the government's core supporters in the country's rural heartland, political analysts said. Somchai's backers had condemned the verdict in advance as a "judicial coup" mounted by a biased court, raising fears that pro-government crowds might come out en masse, leading to clashes.

"This will relieve some of the pressure, and it could provide more alternative ways out of this crisis. But there is still a long way to go," said Panitan Wattanayagorn, a political science professor at Chulalongkorn University in Bangkok.

Government supporters had complained that the court declined to hear witness testimony, and a number of observers questioned the fact that the long, typewritten verdict was read out less than an hour after attorneys for the parties finished their closing arguments.

"If they put too much pressure on us, then it will be the time for action," demonstrator Cho Dindaeng said outside the court.

Although his supporters were angry, Somchai, who had been prime minister for three months, seemed less concerned.

"My duty is over," Somchai said in the northern town of Chiang Mai, where he had fled to avoid the disruption caused by the anti-government demonstrations. "I am now an ordinary citizen."

The Constitutional Court issued a five-year ban from politics against Somchai and 108 officials from his People Power Party and coalition partners. The penalties stem from alleged electoral fraud in last December's vote, which was won by Somchai's allies. A similar verdict in May 2007 dissolved the political party of ousted prime minister Thaksin Shinawatra, who was removed from office by the Thai military in 2006 amid allegations of corruption. PAD protesters argued that Somchai was a stand-in for Thaksin, his brother-in-law.

Thaksin had upset members of the middle class, Thailand's traditional arbiter of power, by sidelining them with populist policies of loans and cheap health care that were designed to appeal directly to the country's marginalized rural poor. The PAD is a largely urban movement that has received backing from powerful figures in the military and among supporters of Thailand's revered king.

PAD's solution to the Thaksin camp's continuing electoral success has been to push for a limited dismantling of Thailand's democracy. It has floated ideas of partially appointing parliament members or giving professionals the chance to vote for special seats.

The PAD's protests in recent weeks had effectively eliminated the government's ability to run the country, with key buildings -- including the prime minister's compound -- occupied by demonstrators.

Although cargo flights resumed after the court ruling, about 250,000 tourists are still stranded in Thailand as a result of the protests, struggling to get seats on any plane out of a small naval base that is now the country's main gateway to the world. Officials at Suvarnabhumi, the international airport, said they hoped to have it back up and running by Friday.